diff --git a/app/models/category.rb b/app/models/category.rb
index db500e6ff67..2dcdd7d1e86 100644
--- a/app/models/category.rb
+++ b/app/models/category.rb
@@ -889,6 +889,6 @@ end
 #  index_categories_on_reviewable_by_group_id  (reviewable_by_group_id)
 #  index_categories_on_search_priority         (search_priority)
 #  index_categories_on_topic_count             (topic_count)
-#  unique_index_categories_on_name             (COALESCE(parent_category_id, '-1'::integer), name) UNIQUE
-#  unique_index_categories_on_slug             (COALESCE(parent_category_id, '-1'::integer), slug) UNIQUE
+#  unique_index_categories_on_name             ((COALESCE(parent_category_id, '-1'::integer)), name) UNIQUE
+#  unique_index_categories_on_slug             ((COALESCE(parent_category_id, '-1'::integer)), slug) UNIQUE WHERE ((slug)::text <> ''::text)
 #
diff --git a/db/migrate/20191008124357_add_unique_index_categories_on_slug.rb b/db/migrate/20191008124357_add_unique_index_categories_on_slug.rb
index 5ee97c64826..7c9dad67e3b 100644
--- a/db/migrate/20191008124357_add_unique_index_categories_on_slug.rb
+++ b/db/migrate/20191008124357_add_unique_index_categories_on_slug.rb
@@ -5,8 +5,7 @@ class AddUniqueIndexCategoriesOnSlug < ActiveRecord::Migration[6.0]
     add_index(
       :categories,
       'COALESCE(parent_category_id, -1), slug',
-      name: 'unique_index_categories_on_slug',
-      unique: true
+      name: 'unique_index_categories_on_slug'
     )
   end
 end
diff --git a/db/migrate/20191016124059_fix_category_slugs_index.rb b/db/migrate/20191016124059_fix_category_slugs_index.rb
new file mode 100644
index 00000000000..58b67b6fe65
--- /dev/null
+++ b/db/migrate/20191016124059_fix_category_slugs_index.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class FixCategorySlugsIndex < ActiveRecord::Migration[6.0]
+  def change
+    remove_index(:categories, name: 'unique_index_categories_on_slug')
+
+    add_index(
+      :categories,
+      'COALESCE(parent_category_id, -1), slug',
+      name: 'unique_index_categories_on_slug',
+      where: "slug != ''",
+      unique: true
+    )
+  end
+end